The present invention relates to a pressure, on-demand type ink-jet recording apparatus.
Because of their simple constructions, the pressure, on-demand type ink-jet heads have been applied in various fields. One example is a multiple-nozzle print head for copying machines. However, since the driving frequency is within the audio frequency range, sound waves of considerably high intensity are generated when the multiple-nozzle ink-jet heads are operated. In general, the intensity of sinusoidal sound waves is expressed by EQU I=2.pi..sup.2 .rho..nu..sup.2 Va.sup.2
where
.nu.=the oscillation frequency; PA1 .rho.=the density of air; PA1 a=the amplitude; and PA1 V=the velocity of sound.
It is seen that the intensity I is proportional to the square of the amplitude a. When there exists the number of n sinusoidal sound waves of the same amplitude, frequency and phase, the intensity In becomes EQU In=2.pi..sup.2 .rho..nu..sup.2 v(na).sup.2 =n.sup.2 I
That is, the intensity is increased in proportion to the square of the number of sinusoidal sound waves. As a result, when constructive interferences of sound waves produces by the pressure waves which in turn are generated by respective print head or nozzle units should occur, slightly objectionable noise results.